Instantaneous Voltage Regulated Seamless Transfer Control Strategy for Utility-interconnected Fuel cell Inverters with an LCL-filter

This paper proposes a new control strategy for the transition between grid-tied mode and off-grid mode of the utility interconnected fuel cell inverters with an LCL filter. During the transition from grid-tied mode to stand-alone mode, the inverter control is switched to voltage-controlled mode from the beginning of the transition, using inverter instantaneous output voltage regulation to reduce the output grid current of the inverter quickly, so that the static transfer switch is turned off immediately and the inverter maintain a continuous voltage output. It will result in a short transition time and minimum voltage fluctuation on the load. The algorithm is described along with their transition performances. Simulations and experiments on a 5 kW fuel cell inverter prototype are provided to validate the algorithm